Euclid’s mission to explore the darkest secrets of the universe

France Press agency , Posted on Saturday, February 25, 2023 at 05:19

The European Euclid space telescope is still housed in a sterile room, in Cannes, decorated in a sun-coloured dress. In a few months, it will be blasting into space in an effort to shed light on two of the great mysteries of the universe: dark matter and dark energy.

These two elements, completely theoretical and invisible, make up 95% of the universe, but we know almost nothing about their exact nature. A lack of knowledge that mission chief Giuseppe Racca describes as a “cosmic embarrassment”.

Dark matter is thought to explain, among other things, why galaxies are not spread out in swarms of stars. As for dark energy, its existence is necessary to explain the acceleration of the expansion of the universe.

In an effort to lift the veil over these mysteries, the European Space Agency (ESA) mission will map the universe in 3D, encompassing two billion galaxies over a one-third part of the visible sky.

The third dimension of the map will be time. Because by capturing the light of galaxies that took up to ten billion years to reach us, Euclid will plunge into the distant past of the universe, which was born 13.8 billion years ago.

The two-ton vessel, 4.7 meters high and 3.5 meters wide, was presented to the press for the first time this week, in a clean and sterile room, belonging to the Thales Alenia aerospace group, in Cannes.

– Absenteeism measure –

He will still have a few more tests before he leaves for Cape Canaveral, Florida. It will be launched on a SpaceX Falcon 9 rocket, between July 1 and 30. The originally planned flight on a Russian Soyuz rocket was canceled due to sanctions imposed on Russia following its invasion of Ukraine.

Euclid will reach a location close to the James Webb Space Telescope, 1.5 million kilometers from Earth, ensuring that it will always be exposed to the sun from the solar panels.

Its first images are expected next October, but it will take much longer for any discoveries, after analyzing the mountains of data that Euclid will provide.

The head of the mission explained to the press that the European mission, at a cost of 1.5 billion euros, should continue until 2029, with a few years of reward “if nothing extraordinary happens.”

How would Euclid – who owes his name to the father of geometry – continue to observe the invisible? measure of his absence.

Light from a very distant object, such as a galaxy, is deflected imperceptibly by the visible matter and dark matter it encounters on its way to the observer. This is the effect of weak gravitational lensing.

– wavering understanding –

Subtracting visible matter, Giuseppe Racca says, “we can + calculate + the presence of dark matter that exists between” the distant object and the observer.

For this purpose, Euclid has two instruments: a telescope with a diameter of 1.2 meters and an infrared spectrophotometer and photometer (NISP).

Euclid has the peculiarity of viewing its observing field, which is equivalent to the surface of “two full moons,” notes David Elbaz, an astrophysicist with the Atomic Energy Commission (CEA).

This field will allow Euclid to identify massive structures – such as black holes – that the James Webb telescope cannot identify because “its observational field is too small”, explains to AFP the scientific director of the project. Rene Lorig.

Our understanding of the universe is still flawed. For example, two very accurate measurements of the expansion rate of the universe currently give two different answers: an asymmetry called the Hubble tension, in which dark energy could play a role.

And this week, the James Webb telescope discovered six galaxies much more massive than expected, in the distant ages of the universe (between 500 and 700 million years after the Big Bang).

Euclid could be the “only tool” capable of answering these questions, according to David Elbaz.